Regions · California

Due to its vehicle regulations that preceded the Federal Clean Air Act (CAA) of 1970 and particularly severe motor vehicle-related air quality problems, the state of California retains the unique authority to set emission standards that are more stringent than federal standards. Section 177 of the Clean Air Act authorizes other States to adopt California’s more stringent standards. Currently, 15 States have done so. The California Air Resources Board and the California EPA are the regulatory bodies that are primarily responsible for upholding California’s air quality and transportation regulations. Vehicle emissions are regulated through the LEV (Low Emission Vehicle) program, which served as the basis for U.S. Tier 2 and 3 standards. California has also developed optional low-NOx standards for heavy-duty vehicles. Other programs include the Low-Carbon Fuel Standard, which sets GHG limits for transportation fuels.